<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>最多能完成排序的块</title>
</head>
<body>
  <script>
    function fn(arr) {
      let m = 0, res = 0;
      for (let i = 0; i < arr.length; i++) {
        m = Math.max(m, arr[i]);
        if (m === i) {
          res++
        }
      }
      return res
    }
    console.log(fn([4, 3, 2, 1, 0]))
  </script>
</body>
</html>